The present invention concerns a method for automatic adjustment of the initial height of a flame cutter, particularly an electron or plasma torch, for a workpiece with an irregular surface, which is preferably arranged below a liquid level.
Further the invention relates to a mechanism for implementation of such method. A procedure for maintaining constant distance of a plasma cutter from a workpiece arranged under a liquid level is known from German Patent DE-OS 27 06 232, whereby, for the purpose of distance adjustment, the electrical potential of the electric cutting arc is determined, compared in a reference input element with an index value, and the deviation determined in this manner is conveyed to a height adjustment mechanism for the plasma torch for height correction. In this procedure, which is preferably used for plasma cutting of a workpiece arranged under a liquid level, it is necessary, at the beginning of the cutting process, that the plasma torch is first positioned at a specific initial height of the workpiece, so that the electric cutting arc may then be activated. To date, as can be seen from DE-OS 27 06 232, this initial height, which is dependent on the energy of the cutting art, that is, on the performance of the plasma torch used, has been set manually or automatically via corresponding adjustment devices.
Considering that the workpiece is placed under water and also the viewing conditions resulting from this fact, a hand adjustment is unsatisfactory. A procedure for automatic adjustment of the initial height of a flame cutter is known from German Patent DE-AS 24 27 694, according to which the flame cutter with an attached sensor is first moved towards the workpiece until the sensor touches the workpiece. Subsequently, the cutter is moved back to the desired initial height. This procedure requires a return movement of the cutter and is consequently time consuming.